1. Field of the Invention
The present disclosure relates to an injection apparatus, and, more particularly, to an injection apparatus, which allows vulcanization of a material injected into an injection mold to occur uniformly and rapidly within the injection mold, thereby improving a quality of an injection molded product while increasing a speed of an injection operation.
2. Description of the Related Art
An injection apparatus refers to an apparatus which produces an article having a desired shape by injecting a raw material, such as a rubber or plastic material, having fluidity at high temperatures, into an injection mold having a predetermined shape corresponding to the desired shape of the product, followed by cooling the raw material.
A conventional injection apparatus disclosed in Korean Utility Model Registration No. 20-0169063 comprises an upper frame, a lower frame, an injection mold disposed between the upper and lower frames, and a raw material feeder positioned at one side of the upper frame, wherein the upper frame is provided with an injection chamber to receive the raw material supplied into the upper frame from the raw material feeder, and with a nozzle to guide movement of the raw material into the injection mold.
Above the nozzle, an injection plunger is positioned to compress the raw material to be injected into the nozzle through the injection chamber, and an injection cylinder to generate driving force to move the injection plunger up and down.
The upper frame is provided at a lower portion with an upper heater, and the lower frame is provided at an upper portion with a lower heater such that a mold is positioned between the upper and lower heaters. The mold is divided into an upper mold and a lower mold so that the upper mold is brought into contact with the upper heater and the lower mold is brought into contact with the lower heater.
With this construction, as the injection apparatus is operated, a raw material is induced into the injection chamber by the raw material feeder, and when the injection cylinder is operated, the injection plunger is lowered, causing the raw material to be induced into the nozzle.
After moving along the nozzle, the raw material is injected into the mold connected to an end of the nozzle. When the heaters provided to the upper and lower portions of the mold are operated to generate heat, the heat is transferred from the heaters to the raw material via the mold. At this point, the heaters heat the raw material, for example, a rubber, to a temperature suitable for vulcanization in the mold.
The term “vulcanization” refers to a reaction to impart elasticity to the rubber by coupling sulfur to structure of the rubber. At this point, a predetermined amount of heat is required for chemical coupling of the sulfur, simply mixed with the rubber, to the structure of the rubber. In this regard, according to the conventional injection apparatus, heat for the vulcanization is supplied from the heaters.
Meanwhile, since the raw material, in particular, the rubber, has a relatively low thermal conductivity, heat can be efficiently transferred to a portion of the raw material along an inner surface of the mold, which contacts the raw material. However, the heat cannot be efficiently transferred to a portion of the raw material near a central region of the mold, causing a temperature deviation in the raw material.
Hence, since it is necessary to wait until the heat is transferred to the central region of the mold in order to allow the vulcanization of the raw material to occur in an overall region within the mold, there is a problem of extending a time for injection operation.
In addition, although an outer surface of an injected product may have a desired elasticity even with insufficient transfer of heat into the central region of the raw material, an interior of the product cannot have the desired elasticity, failing to achieve a uniform quality.
Furthermore, a low thermal conductivity of the raw material causes local overheating of the raw material within the mold, thereby causing local acceleration of vulcanization, which results in defects such as flow-marks on an outer surface of the product.
Accordingly, there is a need for an injection apparatus that overcomes, alleviates, and/or mitigates one or more of the aforementioned and other deleterious effects of prior art injection apparatuses.